This invention relaters general to display s),stems and, more specifically, to a rear projection display system that minimizes luminosity differences to the viewer.
In viewing systems, and particularly in those viewing systems where multiple images are projected onto a screen the uneven emergence of light from the screen creates bright spots in the screen images seen by the viewer. Typically, Fresnel lens are used in projections systems for such purposes as magnifying the image or to limit the amount of incident light.
In the present invention, the Fresnel lens segments are angularly positioned so as to minimize luminosity difference on the screen. That is, be angularly positioning the light transmission segments within the Fresnel lens one can deflect the incoming light rays, which enter the Fresnel lens at different angles, so that all the light rays emerge from the Fresnel lens at the same angle. In the present invention the combined effect of the angular positioning of each of the viewing segments in the Fresnel lens and the internal refraction tofu the light by the Fresnel material can be controlled to bend the light rays passing through each segment so that the light rays exiting the Fresnel lens exit an angle which is parallel to each other.
U.S. Pat. No. 4,482,206 shows a rear projection television screen that uses two Fresnel lens and maintains the angle of incident of light to less than 40 degrees to reduce the amount of reflected light.
U.S. Pat. No. 4,695,135 discloses an information display panel wherein a Fresnel lens is placed on the front surface of an array of television screens to create a large scale television screen.
U.S. Pat. No. 4,152,047 discloses a projection screen using a Fresnel lens where the optically inactive surfaces are approximately parallel with the incoming rays.
U.S. Pat. No. 4.076,384 discloses a rear projection system using a Fresnel lens to direct more light toward the viewers eye.
U.S. Pat. No. 5,313,326 discloses the use of a Fresnel mirror in an automobile.
U.S. Pat. No. 5,390,050 discloses forming in eccentric Fresnel lens from a concentric Fresnel lens.
U.S. Pat. No. 5,864,431 discloses a method of eliminating or reducing distortion using a Fresnel lens.
U.S. Pat. No. 3,628,854 discloses a flexible Fresnel lens that can be adhered to an ophthalmic lens.
U.S. Pat. No. 3,982,822 discloses a composite Fresnel lens assembly.
U.S. Pat. No. 4,293,196 discloses an objective lens system with an aspherical Fresnel lens.
Briefly, the present invention comprises a rear projection system having a display screen and a Fresnel lens wherein the each of the incident faces of the viewing segments of the Fresnel lens are angularly positioned so that incoming light rays, which enter each of the viewing segments at different angles, are reflected by each of the segments so that the light rays from each of the viewing segments emerge in a direction parallel to each other to thereby limit luminosity differences in images viewable on the display screen.